#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

int decode(unsigned char);

int decode(unsigned char ch) {
 ch = ~((ch << 2) | ((ch & 0xC0) >> 6));
 if (ch) {
  if (isprint(ch)) {
   return ch;
  } else {
    return ' ';
  }
 }
 return '\n';
}    

int main(int argc, char *argv[]) {
int ch;
FILE *fp;

 if (argc < 2) {
  fp = stdin;
  } else {
   if (NULL == (fp = fopen(argv[1], "r"))) {
     fprintf(stderr, "Error: Cannot open file %s\n", argv[1]);
     exit(EXIT_FAILURE);
    }
  }

 while (EOF != (ch =fgetc(fp))) {
  fputc(decode(ch), stdout);
 }
 return EXIT_SUCCESS;
}

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